How Do Wood-Fired Hot Tubs Work? UK Buyers Guide

Reviewed by the Palmako UK content team with insights from our garden building experts.

A wood-burning hot tub is simply in a class of its own, and these days, they’re an excellent option for homeowners wanting to create a ‘staycation’ experience at home. 

However, before the nostalgia of a wood-burning stove combined with bubbling water becomes irresistible, you need to understand how a wood-fired hot tub works. This will help you make the right choice for your outdoor space and ensure you enjoy your hot tub experience in every season. 

Quick Overview

Wood-fired hot tubs are made from wood, fibreglass and aluminium, with either an internal or an external wood-burning stove. They use natural circulation (thermosiphon) to move water and heat it, and therefore do not require electric pumps. It takes approximately 1-2 hours to heat the tub to 38 degrees Celsius. 

Table of Contents

• How does a wood-fired hot tub heat water?
• Integrated vs. external stove
• Wood-fired hot tub: Usage and maintenance
• Wood-fired hot tubs vs electric hot tubs
• Cost considerations
• Conclusion
• FAQs

How does a wood-fired hot tub heat water?

The appeal of wood-fired tubs lies in their use of natural materials, wood-burning stoves, and their ability to heat water through convection. This eliminates the need for electric heaters, making wooden tubs more energy efficient.  

Wood-burner hot tubs use the thermosiphon principle to circulate water through the burner system, changing the water temperature. This creates a simple feedback loop that works as follows:

• After filling the hot tub with water, wood is placed inside the firebox (stove) and ignited.
  
  
• The fire will heat the water inside a metal jacket or coil (depending on the type of hot tub).
  
  
• As a result of the heating process, hot water rises and flows into the tub, while cooler water is drawn into the heating system. 
  
  
• This continuous loop draws cold water and releases hot water, heating the tubs to the desired temperature. Reaching an optimal temperature can take between 1 and 4 hours, depending on the fuel quality, the tub's size and the materials it is made from. 

Certain wood-fired tubs can heat water within 1-2 hours. They feature ergonomic fibreglass interiors (which are also more hygienic) and integrated woodburners. For example, Palmako hot tubs are built to this design and can heat 1150L of water to 38 degrees Celsius in 2 hours. Compare this to a six-kilowatt high-performance electric heater, which takes 5.5 hours to heat the same amount of water. This makes the wood-fired tub the superior choice for efficient heating. 

Integrated vs. external hot tub stove

An integrated hot tub stove is one in which the firebox sits inside the tub, either partially or fully submerged. An external hot tub stove is one in which the stove is outside the tub and connected to the tub via two pipes. 

Wood-fired hot tub: Usage and maintenance

Creating realistic expectations about what it's like to own a wood-fired outdoor hot tub is important for long-term enjoyment of your purchase. The wooden hot tub is not a ‘set-and-forget’ process. It is better compared with the ritual of preparing a BBQ. A typical session will look like this:

• Check that the stove is clean and ash-free, then fill the tub with water. 
  
  
• Using kindling and small logs, ignite the fire and open the air vents.
  
  
• Add logs to the stove every 20-40 minutes. This stage can last up between 2 and 4 hours. Monitor the water temperature and stir to evenly distribute the heated water. 
  
  
• Reduce airflow during usage and add smaller logs to sustain the heat rather than stoke it. 
  
  
• Let the fire burn out naturally when the session is over. 

Unless you purchase a hot tub with a built-in thermometer, consider buying one for more accurate temperature control. A wood-burning tub requires attention while in use, and a thermometer is an easy way to monitor the temperature.

A wood-burning hot tub is about creating an experience that lasts a few hours, rather than a quick ‘dip’. The cost of running your hot tub will be less than that of an electric hot tub, but the costs can be unpredictable and vary depending on the type of wood and how many sessions you have per week. 

Maintenance is straightforward and should not be skipped if you want to keep your hot tub in peak condition. Just like a BBQ, clean-up is part of the ritual of using the tub. After each session, you will need to remove the ash and check for any blockages in the chimney. Water should be drained after 2-3 uses; if possible, drain it more often and clean the surfaces to prevent contamination. You can also chemically treat water if you don’t want to drain it after every use. 

Expert insight: Hot tub safety is often at the top of buyer concerns. Many of these concerns can be managed with correct use. There are three safety areas that you pay attention to: Temperature monitoring, proper chimney ventilation, and never light the stove without water in the tub. Children should be supervised by an adult when they are in or around the tub.

Wood-fired hot tubs vs electric hot tubs

The main difference between a wood-fired hot tub and an electric hot tub is that a wood-fired tub does not use electricity. However, there are also differences in heating speeds and running costs. 

Wood-fired hot tubs are hybrid assemblies. The outer shell is made of high-quality timber such as Nordic spruce, thermowood or exotic hardwoods (teak/oak/redwood). The inner shell can be fibreglass, vacuum-molded plastics, or marine-grade aluminium. The heating system is made of a metal such as aluminium or steel. 

A wooden hot tub with a stove can use any type of wood, but manufacturers recommend kiln-dried or hardwood. If you use moist wood, up to 30% of the fire's energy is used to evaporate water, making the heating system inefficient. Each time you fire up your hot tub, you will need 12-25kg of wood logs (or 2-3 armloads). 

Electric tubs depend on a closed-loop system and therefore use different materials. The shell is made from acrylic or rotomoulded polyethylene. This shell is enclosed in a hot tub frame made of wood slats, covering a metal frame. The heating and circulation system consists of an electric heater and pump combination. In the UK, most household electric heaters are 2–3 kW. These heaters take much longer to heat up than a wood-fired tub.

When should you opt for a wood-fired tub vs an electric tub?

Wood-fired tubs are the perfect complement for off-grid properties and those who appreciate a more natural hot tub experience. They are also good for anyone looking to keep electricity bills low and for properties where outdoor electrical installations aren't permitted. Electric hot tubs are a good option when cost considerations are not your top priority, and you require a predictable heating process or the use of jets in your hot tub. 

Cost considerations

In the UK, there are several cost considerations when purchasing and operating a wood-burning hot tub. Here are the average costs for 2026.

Conclusion

Wood-burning hot tubs offer a very different experience from conventional electric tubs. They prioritise simplicity and create a slower, more relaxed outdoor experience that doesn't require electricity or technology. Preparing a wood-fired tub becomes part of the experience, rather than just a step before using it. Wood-fired hot tubs can also be paired with a sauna or cold plunge, creating a traditional outdoor retreat for the entire family.

Wood-fired tubs are perfect for off-grid living, a relaxing garden retreat, or that secluded spot in your garden. When you’re ready, speak to Palmako’s highly experienced consultants, or you can browse their hot tub catalogue and order online. 

FAQs: How do wood-fired hot tubs work?

1. How do wood-fired hot tubs work?

Wood-fired hot tubs work by burning logs, either in an integrated stove or an external stove connected to the tub by pipes. Convection is responsible for heating the water as cold water flows into the heating system and is pushed out into the tub. This process continues to heat the water as long as fuel (logs) is available. This process takes between 1.5 and 3 hours, and once the desired temperature is reached, smaller logs can be used to maintain it. 

2. Are wood-fired hot tubs safe?

Wood-fired hot tubs are considered safe when buyers follow a few safety tips. Monitor temperature with a thermometer and keep it below 38-40 degrees Celsius. Ensure plenty of chimney ventilation, and don’t light the stove without water in the tub. Adult supervision is advised when children are present.

3. Is a wood-burning hot tub difficult to maintain?

A wood-burning hot tub is not difficult to maintain, but it requires cleaning and maintenance between sessions. Water will need to be changed between 1-3 uses, and ash will need to be cleaned out of the stove. A more thorough cleaning will be required after three uses to prevent biofilm and water contamination. 

3. Can a wood-fired hot tub overheat?

Yes, a wood-fired hot tub can overheat because it lacks automated temperature control. They need constant temperature monitoring. When the optimal heat has been achieved, it is best to stop adding fuel to the stove and let the tub cool down naturally. If you want to prolong a hot tub session, it is advisable to add small logs to maintain heat rather than stoking the fire. 

4. Are wood-fired tubs better than inflatable hot tubs?

Permanent wood-fired tubs and inflatable hot tubs serve different purposes, and therefore, it is difficult to compare them directly. Inflatable hot tubs are better suited for homeowners who can’t (or don’t want to) erect permanent structures in their garden. Inflatable hot tubs are also generally cheaper than wood-fired tubs. A wood-burning tub is better if you want a permanent, off-grid option that doesn’t require any electricity.